Poly(ethylene oxide) of molecular weight from about 600,000 undergoes degradation during thermoplastic processing when exposed to heat and shearing forces resulting in chain scission and consequently a loss of physical properties. Substantial reductions in molecular weight are observed during such processing operations. The chain scission occurs rapidly causing poly(ethylene oxide) compounds to lose their strength and in many instances become extremely tacky. Experience has shown that conventional thermoplastic processing of poly(ethylene oxide) compositions with a molecular weight above about 600,000 can result in polymer degradation before the processing is complete.
To remedy this situation, poly(ethylene oxide) formulations have been stabilized with phenothiazine and plasticized with the ethylene oxide adduct of nonylphenol. However, for poly(ethylene oxide) whose molecular weight exceeds 600,000, the addition of a mixture of phenothiazine and the ethylene oxide adduct of nonylphenol does not provide the desired stability when the poly(ethylene oxide) compositions are calendered into films. Another problem encountered is the fact that poly(ethylene oxide) compositions containing a mixture of phenothiazine and the ethylene oxide adduct of nonylphenol are not recognized for applications where the composition may be ingested by humans. Also, films which contain phenothiazine may undergo substantial discoloration during storage.
Compositions of poly(ethylene oxides) having molecular weights greater than 600,000 which can be formed into shaped articles are becoming commercially important.